1. Field of the Invention
The present invention relates to a rotary piston engine and, more particularly, to an improvement in a rotary piston engine with respect to the fuel consumption rate and exhaust gas purification.
2. Description of the Prior Art
In the Wankel type rotary piston engine comprising a casing composes of a rotor housing which has a trochoidal inner peripheral surface and side housings which close opposite ends of said rotor housing, and a polygonal rotor adapted to rotate eccentrically in said casing with its apex portions sliding over said trochoidal inner peripheral surface, the flame initiated by an ignition plug propagates at a very high speed toward the leading side located at the rotational forward end of the rotor by the effect of the flow of the fule-air mixture caused by the rotation of the rotor and thus the flame does not propagate well toward the trailing side located at the rearward end of the rotor. Therefore, the fuel-air mixture is combusted well at the leading side while the mixture is not completely combusted at the trailing side thereby causing a relatively low combustion efficiency and a relatively high fuel consumption accompanied by an additional drawback that the emission of harmful uncombusted components such as CO and HC is relatively high.
To solve the abovementioned problem, an improved rotary piston engine has been developed wherein a relatively rich fuel-air mixture is supplied at the leading side where fuel-air mixture is easily combusted while only air is supplied at the trailing side where the combustion of a fuel-air mixture is not favorably effected so that a combustion chamber of the engine is charged with two separate layers of fuel-air mixture and air, as is disclosed in Japanese Patent Application No. 71426/74 filed by the same assignee as the present application. This rotary piston engine comprises a first intake port which opens in the trochoidal inner peripheral surface of the rotor housing and a second intake port which opens in the inner surface of the side housing at a position advanced from said first intake port as seen in the rotational direction of the rotor wherein the fuel-air mixture is supplied from said first port while only air is supplied from said second port.
Now, in this connection, in a rotary piston engine wherein the entire or a part of the intake fuel-air mixture or air is supplied through a peripheral port which opens in the trochoidal inner peripheral surface of a rotor housing, there occurs a pulsation in the intake flow through the peripheral port which causes a reverse flow of the fuel-air mixture including exhaust gas blown from the peripheral intake port toward the intake passage during an intake stroke, when the engine is operated in a low speed and low load condition. If the reverse flow of the fuel air mixture including the exhaust gas occurs, the intake efficiency lowers and, furthermore, a pulsating flow is induced in the air passage of the carburetor thereby causing poor fuel consumption. To solve this problem, according to the present invention a check valve is provided in the intake passage which leads to the peripheral intake port, as disclosed in Japenese Patent Application No. 3542/75 filed by the same assignee as the present application to whom the former invention has been assigned.